The present invention, in some embodiments thereof, relates to lenticular printing and, more particularly, but not exclusively, to lenticular image articles and methods for reducing or eliminating banding artifacts in lenticular printing products such as lenticular image articles.
Lenticular printing is a process consisting of creating a composite interlaced image by interlacing various images, and attaching it with a lenticular lens arrangement, such as a sheet, to form a lenticular image article. When digitally processing the composite interlaced image, various images are collected are flattened into individual, different frame files, and then digitally combined by interlacing into a single final file in a process which may be referred to herein as interlacing. The lenticular printing can be used to create a dynamic image, for example by offsetting the various layers at different increments in order to give a three dimension (3D) effect to the observer, various frames of animation that gives a motion effect to the observer, a set of alternate images that each appears to the observer as transforming into another. One of the most common methods of lenticular printing, which accounts for the vast majority of lenticular images in the world today, is lithographic printing of the composite interlaced image directly onto lower surface of a lenticular lens sheet.
In order to improve the clarity of the effect of the dynamic image to the observer, some artifacts may be reduced. One of the reduced artifacts, is banding. In some cases, the banding artifact is formed when transition starts in several places and progresses from each starting point towards the next, giving the impression of several curtains crossing the visual. The unwanted bands appear typically in parallel to the lens direction. The banding may be caused because of a mismatch between the printing resolution, denoted herein as D, and the lenticular sheet pitch, denoted herein as P, such that D/P is a non-integer number.
One of the known methods for reducing banding is adding blur to the composite interlaced image which can be implemented for example by interlacing not only the set of input images but also an additional set of so-called separator images. These separator images are created, for example, as an averaging of the input images. It should be noted that the use of separator images increases the mixing among views and hence increases ghosting and blur and provides only a partial reduction in the banding artifact.
Another known method for reducing banding is modifying the resolution of the printing system to match the lenticular sheet pitch, for example by changing the distances of laser dots in an offset plate setter. This is possible to do only in printing systems with variable resolution.